For many years, concrete column forming tubes have been utilized and have been constructed of spirally-wound plies of paper adhered together and defining an inside wall surface of predetermined diameter which is coated with plastic material for concrete release properties. This plastic coating was usually provided by coating one side of the paper plies prior to spiral winding of the tube. These forming tubes received poured concrete therein which dried and set-up to produce a concrete column. The forming tube was then striped away from the concrete column and this operation was aided by the release properties of the plastic coating on the inside of the tube to leave a finished concrete column. These types of prior art tubes are illustrated in U.S. Pat. Nos. 2,677,165 and 2,914,833, for example, which are assigned to the assignee of the present invention.
Due to the spirally-wound construction of these forming tubes, spiral seam lines and other undesirable surface characteristics were usually present on the inside wall surface of the forming tube which resulted in spiral seam lines and other irregularities molded on the outside surface of the produced concrete column. From an aesthetic standpoint, these spiral seam lines and other irregularities were often undesirable on the produced concrete column and sandblasting or other finishing techniques were necessary to produce a smooth outside surface on the concrete columns.
In an effort to overcome these problems, separately-formed flexible cylindrical liners have been proposed by U.S. Pat. No. 4,595,168 and Assignee's U.S. Pat. No. 4,957,270. These separate liners were inserted into the concrete column forming tube after manufacture of the tube and often at the concrete column forming site. While these separate liners improved the surface quality of the resulting concrete column, they did often produce one vertical seam line running the length of the formed column, were expensive to manufacture, difficult to maintain and install and presented other problems in the manufacture and use thereof.